Semiconductor photo-detecting device

ABSTRACT

A photo-detecting device includes a first nitride layer, a low-current blocking layer disposed on the first nitride layer, a light absorption layer disposed on the low-current blocking layer, and a Schottky junction layer disposed on the light-absorption layer. The low-current blocking layer includes a multilayer structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 10-2013-0113854, filed on Sep. 25, 2013, which isincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

1. Field

Exemplary embodiments relate to a semiconductor photo-detecting device.More particularly, exemplary embodiments relate to a semiconductorphoto-detecting device with excellent detection efficiency for aspecific wavelength of light.

2. Discussion of the Background

Semiconductor photo-detecting devices operate on the principle thatcurrent is induced by illuminated light. In particular, semiconductorphoto-detecting devices for detecting ultraviolet (UV) light may be usedin a variety of fields, such as business, medical science, defenseindustry, communications, etc. The semiconductor photo-detecting devicesare based on the principle that a depletion region is formed by theseparation of electrons and holes within a semiconductor upon absorptionof photons, and current is, thus, induced depending upon a flow of theelectrons.

Semiconductor photo-detecting devices using silicon have been typicallyused in the art. However, the semiconductor photo-detecting devices mayrequire high voltage for operation and have low detection efficiency.Particularly, when the semiconductor photo-detecting devices fordetecting UV light are manufactured using silicon, photo-detectionefficiency may decrease due to the silicon being sensitive not only toUV light but also to visible and infrared light. In addition, UV lightdetecting devices using silicon may be thermally and chemicallyunstable.

To address such issues, photo-detecting devices using nitride-basedsemiconductors have been developed. Photo-detecting devices usingnitride-based semiconductors may have relatively high responsivity, highreaction rate, low noise level, and high thermal and chemical stabilitycompared with photo-detecting devices using silicon. Photo-detectingdevices using AlGaN, among nitride-based semiconductors, as a lightabsorption layer may show improved characteristics as a UV lightdetecting device.

Nitride-based semiconductor photo-detecting devices may be manufacturedin a variety of structures, such as, photoconductors, Schottky junctionphoto-detecting devices, p-i-n photo-detecting devices, and the like.Among the various forms of nitride-based semiconductor photo-detectingdevices, Schottky junction photo-detecting devices may include asubstrate, a buffer layer on the substrate, a light absorption layer onthe buffer layer, and a Schottky junction layer on the light-absorptionlayer. Further, a first electrode and a second electrode may be arrangedon the Schottky junction layer and the buffer layer or thelight-absorption layer, respectively. To use the Schottky junctionphoto-detecting device as a UV light detecting device, the lightabsorption layer may be formed of a nitride-based semiconductor havingband gap energy capable of absorbing UV light. Accordingly, AlGaN may beused as a semiconductor substance in the light-absorption layer. A GaNlayer may be used as the buffer layer.

In a structure including an AlGaN light absorption layer and a GaNbuffer layer, when the AlGaN light absorption layer has an Alcomposition of 25% or more, or a thickness of 0.1 μm or more, cracks maybe generated in the light absorption layer, thereby causing a yielddecrease. To prevent cracking in the light-absorption layer, an AlNlayer may be interposed between the GaN buffer layer and the AlGaN lightabsorption layer. Even in this case, photo-detection response may bereduced due to high energy band gap and insulation characteristics ofthe AlN layer. Specifically, when the thickness of the AlN layer is lessthan about 100 Å, photo-detection characteristics may be improved but itmay be difficult to completely prevent cracks, and when the thickness ofthe AlN layer exceeds about 100 Å, cracks may be prevented, butphoto-detection characteristics may be deteriorated.

In addition, GaN, InGaN, and AlGaN layers used as a light absorptionlayer in typical nitride-based semiconductor photo-detecting devices mayhave intrinsic defects and allow current flow in the devices in responseto visible light, but not UV light due to such defects. In response,characteristics of the semiconductor photo-detecting device, a lowUV-to-visible rejection ratio of about 10³ has been measured. That is,the typical semiconductor photo-detecting devices may allow low currentflow in response to visible light but not UV light, thereby,deteriorating detection accuracy.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the inventive concept,and therefore, it may contain information that does not form any part ofthe prior art that is already known in this country to a person ofordinary skill in the art.

SUMMARY

Exemplary embodiments provide a photo-detecting device having highphoto-detection efficiency for light in a specific wavelength range,such as, a UV light wavelength range.

Exemplary embodiments of provide a photo-detecting device including alight absorption layer with improved crystallinity and having highphoto-detection efficiency for, for instance, UV light.

Additional aspects will be set forth in the detailed description whichfollows, and, in part, will be apparent from the disclosure, or may belearned by practice of the inventive concept.

According to exemplary embodiments, a photo-detecting device includes: afirst nitride layer; a low-current blocking layer disposed on the firstnitride layer, the low-current blocking layer including a multilayerstructure; a light absorption layer disposed on the low-current blockinglayer; and a Schottky junction layer disposed on the light absorptionlayer.

According to exemplary embodiments, a method of manufacturing aphoto-detecting device, the method includes: forming a first nitridelayer; forming a low-current blocking layer including a multilayerstructure on the first nitride layer; forming a light absorption layeron the low-current blocking layer; and forming a Schottky junction layeron the light absorption layer, wherein the low-current blocking layer isformed at a lower temperature than the light absorption layer.

As described above, exemplary embodiments provide a photo-detectingdevice with relatively low responsivity to visible light by including alow-current blocking layer. Accordingly, the photo-detecting device mayhave an improved UV-to-visible rejection ratio and achieve improvedphoto-detection efficiency and reliability.

In addition, exemplary embodiments provide a photo-detecting device thatincludes a light absorption layer having improved crystallinity and mayreduce a micro-current induced by reaction to visible light.

The foregoing general description and the following detailed descriptionare exemplary and explanatory and are intended to provide furtherexplanation of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the inventive concept, and are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments of the inventive concept, and together with the descriptionserve to explain the principles of the inventive concept.

FIGS. 1 and 2 are, respectively, a sectional view and a top view of aphoto-detecting device, according to exemplary embodiments.

FIGS. 3, 4, 5, 6, 7, and 8 are sectional views of a photo-detectingdevice at various stages of manufacture, a photo-detecting deviceaccording to exemplary embodiments.

FIG. 9 is a graph comparing characteristics of a photo-detecting device,according to exemplary embodiments.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments. It is apparent, however,that various exemplary embodiments may be practiced without thesespecific details or with one or more equivalent arrangements. In otherinstances, well-known structures and devices are shown in block diagramform in order to avoid unnecessarily obscuring various exemplaryembodiments.

In the accompanying figures, the size and relative sizes of layers,films, panels, regions, etc., may be exaggerated for clarity anddescriptive purposes. Also, like reference numerals denote likeelements.

When an element or layer is referred to as being “on,” “connected to,”or “coupled to” another element or layer, it may be directly on,connected to, or coupled to the other element or layer or interveningelements or layers may be present. When, however, an element or layer isreferred to as being “directly on,” “directly connected to,” or“directly coupled to” another element or layer, there are no interveningelements or layers present. For the purposes of this disclosure, “atleast one of X, Y, and Z” and “at least one selected from the groupconsisting of X, Y, and Z” may be construed as X only, Y only, Z only,or any combination of two or more of X, Y, and Z, such as, for instance,XYZ, XYY, YZ, and ZZ. Like numbers refer to like elements throughout. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Although the terms first, second, etc. may be used herein to describevarious elements, components, regions, layers, and/or sections, theseelements, components, regions, layers, and/or sections should not belimited by these terms. These terms are used to distinguish one element,component, region, layer, and/or section from another element,component, region, layer, and/or section. Thus, a first element,component, region, layer, and/or section discussed below could be termeda second element, component, region, layer, and/or section withoutdeparting from the teachings of the present disclosure.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, may be used herein for descriptive purposes, and,thereby, to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the drawings. Spatiallyrelative terms are intended to encompass different orientations of anapparatus in use, operation, and/or manufacture in addition to theorientation depicted in the drawings. For example, if the apparatus inthe drawings is turned over, elements described as “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. Furthermore, the apparatus maybe otherwise oriented (e.g., rotated 90 degrees or at otherorientations), and, as such, the spatially relative descriptors usedherein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof.

Various exemplary embodiments are described herein with reference tosectional illustrations that are schematic illustrations of idealizedexemplary embodiments and/or intermediate structures. As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should not beconstrued as limited to the particular illustrated shapes of regions,but are to include deviations in shapes that result from, for instance,manufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the drawings are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

Illustrated as examples are composition ratios, growth methods, growthconditions, thicknesses, and the like, for semiconductor layersdisclosed hereinafter, and the following descriptions do not limit theinventive concept disclosed herein. For example, for AlGaN, variouscomposition ratios of Al and Ga may be used according to the need ofthose skilled in the art in the art. Furthermore, semiconductor layersdisclosed hereinafter may be grown by various methods generallywell-known to those skilled in the art, such as Metal Organic ChemicalVapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), Hydride VaporPhase Epitaxy (HVPE), or the like. In the following exemplaryembodiments, semiconductor layers are grown in the same chamber byMOCVD, and sources known to those skilled in the art according tocomposition ratios may be used as sources introduced into the chamber.However, it should be understood that the present invention is notlimited thereto.

FIGS. 1 and 2 are, respectively, a sectional view and a top view of aphoto-detecting device, according to exemplary embodiments.

Referring to FIGS. 1 and 2, a photo-detecting device includes asubstrate 110, a first nitride layer 130, a low-current blocking layer140, a light absorption layer 150, and a junction layer (e.g., Schottkyjunction layer) 160. In addition, the photo-detecting device may furtherinclude a second nitride layer 120, a first electrode 171, and a secondelectrode 173. Although specific reference will be made to thisparticular implementation, it is also contemplated that thephoto-detecting device may embody many forms and include multiple and/oralternative components.

The substrate 110 is disposed at a lower side of the photo-detectingdevice, and any substrate enabling growth of semiconductor layersthereon may be used as the substrate 110. For example, the substrate 110may include at least one of sapphire, SiC, ZnO, and a nitride-basedsubstrate, such as GaN and AN. As described, herein, the substrate 110may include sapphire.

The first nitride layer 130 may be disposed on the substrate 110. Thefirst nitride layer 130 may include a nitride-based semiconductor layer,for example, a GaN layer. The first nitride layer 130 may be doped withimpurities, such as Si, to have n-type properties, or may be undoped. Anitride-based semiconductor may have characteristics of an n-typesemiconductor even in an undoped state, and thus, doping of thenitride-based semiconductor may be determined as needed. When the firstnitride layer 130 is doped with Si impurities to have n-type properties,a doping concentration of Si may be 1×10⁸ or less. The first nitridelayer 130 may have a thickness of about 2 μm.

The second nitride layer 120 may be disposed between the first nitridelayer 130 and the substrate 110. The second nitride layer 120 maycontain a substance similar to that of the first nitride layer 130, and,for example, may include GaN. The second nitride layer 120 may have athickness of about 25 nm and may be grown at a lower temperature (forexample, from 500° C. to 600° C.) than the first nitride layer 130. Thesecond nitride layer 120 may serve to enhance crystallinity of the firstnitride layer 130, whereby optical and electrical characteristics of thefirst nitride layer 130 may be improved by virtue of the second nitridelayer 120. Further, when the substrate 110 is a heterogeneous substrate,such as a sapphire substrate, the second nitride layer 120 may alsoserve as a seed layer on which the first nitride layer 130 may be grown.

The low-current blocking layer 140 is disposed on the first nitridelayer 130 and may have a multilayer structure. The multilayer structureof the low-current blocking layer 140 may include at least one ofbinary, ternary, and quaternary nitride semiconductor layers including(Al, In, Ga)N. Also, at least two nitride layers of the multilayerstructure of the low-current blocking layer 140 may have differentcomposition ratios than one another (or than at least one of the otherlayers of the multilayer structure). Each of the nitride layers may havea thickness of 5 nm to 10 nm, e.g., 6 nm to 9 nm, such as 7 nm to 8 nm.The multilayer structure of the low-current blocking layer 140 may havea structure in which three to ten pairs of nitride layers havingdifferent composition ratios are stacked.

Nitride semiconductor layers included in the multilayer structure of thelow-current blocking layer 140 may be determined depending uponcompositions of nitride layers in the light absorption layer 150. Forexample, when the light absorption layer 150 includes an AlGaN layer,the multilayer structure of the low-current blocking layer 140 may havea structure in which AlN/AlGaN layers and/or AlGaN/AlGaN layers arerepetitively stacked. When the light absorption layer 150 includes anInGaN layer, the multilayer structure of the low-current blocking layer140 may have a structure in which InGaN/InGaN layers, GaN/InGaN layers,and/or AlInGaN/AlInGaN layers are repetitively stacked, and when thelight absorption layer 150 includes a GaN layer, the multilayerstructure of the low-current blocking layer 140 may have a structure inwhich GaN/InGaN layers, InGaN/InGaN layers, and/or GaN/GaN layers arerepetitively stacked.

Each of the nitride layers included in the low-current blocking layer140 may have a different composition ratio by growing the nitride layersat different pressures. For example, if a multilayer structure of thelow-current blocking layer 140 includes an Al_(x)Ga_((i-x))N layer andan Al_(y)Ga_((1-y))N layer repetitively stacked, the Al_(x)Ga_((i-x))Nlayer may be grown at a pressure of about 100 Torr and theAl_(y)Ga_((i-y))N layer may be grown at a pressure of about 400 Torr.When growth conditions are the same except for the pressure, theAl_(x)Ga_((1-x))N layer grown at a lower pressure may have a higher Alratio than the Al_(y)Ga_((1-y))N layer grown at a higher pressure. It iscontemplated, however, than any other suitable method may be utilized tocontrol the various composition ratios of the various nitride layers.

According to exemplary embodiments, the nitride layers grown atdifferent pressures may have different growth rates. As the nitridelayers are grown at the different growth rates, it is possible to reducepropagation of dislocation or to change a propagation path ofdislocation in the process of growth, thereby reducing dislocationconcentration in other semiconductor layers to be grown in subsequentprocesses. Also, different composition ratios of the repetitivelystacked layers may relieve stress caused by lattice mismatch, therebyenhancing crystallinity of the other semiconductor layers to be grown inthe subsequent processes, and preventing damage such as cracks and thelike. In particular, by growing an AlGaN layer having an Al ratio of 15%or more on the low-current blocking layer 140, cracks in the AlGaN layermay be reduced, thereby reducing cracks in the formation of the AlGaNlayer on an AN layer or a GaN layer. According to exemplary embodiments,since the low-current blocking layer 140 including the multilayerstructure may be formed under the light absorption layer 150, the lightabsorption layer 150 may have enhanced crystallinity with reduced crackstherein. When the light absorption layer 150 has improved crystallinity,quantum efficiency of the photo-detecting device may be improved.

The low-current blocking layer 140 may have a higher defectconcentration than the light absorption layer 150. This may be obtainedby growing the low-current blocking layer 140 at a lower temperaturethan the light absorption layer 150. For example, the light absorptionlayer 150 may be grown at a temperature of about 1050° C. and thelow-current blocking layer 140 may be grown at a lower temperature thanthe light absorption layer 150 by 30° C. to 200° C., e.g., 70° C. to160° C., such as 100° C. to 130° C. When the low-current blocking layer140 is grown at a lower temperature than the light absorption layer 150by more than 200° C., crystallinity of the light absorption layer 150formed on the low-current blocking layer 140 may be rapidly degraded,thereby decreasing quantum efficiency of the light absorption layer 150.Thus, the low-current blocking layer 140 may be grown at a lowertemperature than the light absorption layer 150 by 30° C. to 200° C.When the low-current blocking layer 140 is grown at a lower temperaturethan the light absorption layer 150, the low-current blocking layer 140may have a relatively higher concentration of defects, such asdislocation and vacancy, than the light absorption layer 150.Low-current blocking of the low-current blocking layer 140 will bedescribed below in detail.

Referring back to FIG. 1, the light absorption layer 150 may be disposedon the low-current blocking layer 140.

The light absorption layer 150 may include a nitride semiconductorlayer, including at least one of, but not limited to, a GaN layer, anInGaN layer, an AlInGaN layer, and an AlGaN layer. Since an energy bandgap of the nitride semiconductor layer is determined depending upon thetype of Group III element utilized, a substance for a nitridesemiconductor of the light absorption layer 150 may be determineddepending on the wavelength(s) of light to be detected by thephoto-detecting device. For example, a photo-detecting device fordetecting UV light in the UVA band may include the light absorptionlayer 150 including a GaN layer or an InGaN layer. A photo-detectingdevice for detecting UV light in the UVB band may include the lightabsorption layer 150 including an AlGaN layer having an Al ratio of 28%or less, and a photo-detecting device for detecting UV light in the UVCband may include the light absorption layer 150 including an AlGaN layerhaving an Al ratio of 28% to 50%, e.g., 33% to 45%, such as 38% to 40%.However, it should be understood that the present invention is notlimited thereto.

The light absorption layer 150 may have a thickness of about 0.1 μm toabout 0.5 μm, and may be formed to a thickness of 0.1 μm or more toimprove photo-detection efficiency. When the light absorption layer 150is formed on an AN layer or a GaN layer, the light absorption layer 150may suffer from cracking when the light absorption layer 150 includingan AlGaN layer having an Al ratio of 15% is formed to a thickness of 0.1μm or more. As such, device manufacturing yield and photo-detectionefficiency may be reduced from a thin thickness of 0.1 μm or less of thelight absorption layer 150. In contrast, according to exemplaryembodiments, the light absorption layer 150 may be formed on thelow-current blocking layer 140 including the multilayer structure, suchthat cracks may be reduced in the light absorption layer 150. In thismanner, thereby the light absorption layer 150 may be manufactured tohave a thickness of 0.1 μm or more. Accordingly, the photo-detectingdevice according to the exemplary embodiments may have improvedphoto-detection efficiency.

The Schottky junction layer 160 may disposed on the light absorptionlayer 150. The Schottky junction layer 160 and the light absorptionlayer 150 may make Schottky-contact with each other, and the Schottkyjunction layer 160 may include at least one of indium tin oxide (ITO),Ni, Co, Pt, W, Ti, Pd, Ru, Cr, and Au. The thickness of the Schottkyjunction layer 160 may be adjusted in terms of light transmittance andSchottky characteristics, and may be, for example, 10 nm or less.

In addition, the photo-detecting device may further include a cap layer(not shown) between the Schottky junction layer 160 and the lightabsorption layer 150. The cap layer may be a p-type-doped nitridesemiconductor layer containing one or more impurities, such as Mg. Thecap layer may have a thickness of 100 nm or less, e.g., 5 nm or less.The cap layer may improve Schottky characteristics of the device.

Referring back to FIG. 1, the photo-detecting device may include anexposed region of the first nitride layer 130 that may be formed bypartially removing the light absorption layer 150 and the low-currentblocking layer 140. The second electrode 173 may be disposed on theexposed region of the first nitride layer 130, and the first electrode171 may be disposed on the Schottky junction layer 160.

The first electrode 171 may be a metal electrode including multiplelayers, and may be formed from any suitable material. For example, thefirst electrode 171 may include at least one of a Ni layer and an Aulayer stacked. The second electrode 173 may form ohmic-contact with thefirst nitride layer 130 and may include multiple metal layers formedfrom any suitable material. For example, the second electrode 173 mayinclude at least one of a Cr layer, a Ni layer, and an Au layer stacked.It is contemplated, however, that any other suitable formations may beutilized in association with exemplary embodiments described herein.

Hereinafter, a role of the low-current blocking layer 140 according toan operating principle of the exemplary photo-detecting device will bedescribed.

With an external power source connected to the first electrode 171 andthe second electrode 173 of the photo-detecting device, thephoto-detecting device may be prepared in a state in which voltage isnot applied thereto or backward voltage is applied thereto. When lightis radiated to the prepared photo-detecting device, the light absorptionlayer 150 absorbs the light. When the Schottky junction layer 160 isformed on the light absorption layer 150, an electron-hole separationregion, namely, a depletion region is formed at an interfacetherebetween. Electrons created by the radiated light may induce acurrent and a photo-detecting function may be performed by measuring theinduced current.

For example, when the photo-detecting device is a UV light detectingdevice, an ideal UV light detecting device has an infinite UV-to-visiblerejection ratio. However, according to a conventional UV light detectingdevice, a light absorption layer responds also to visible light due todefects in the light-absorption layer and generates electric current.Accordingly, the conventional photo-detecting device may have aUV-to-visible rejection ratio of 10³ or less, thereby causing an errorin the optical measurement.

In contrast, according to exemplary embodiments, the low-currentblocking layer 140 captures electrons created by visible light in thelight absorption layer 150 to decrease the error from the device drivenby the visible light. As described above, the low-current blocking layer140 is grown at a lower temperature than the light absorption layer 150to have a higher defect concentration. Electrons created by visiblelight are much fewer than electrons created by UV light, thereby themovement of the electrons created by visible light may be captured bydefects present in the low-current blocking layer 140. That is, thelow-current blocking layer 140 has such a higher defect concentrationthan the light absorption layer 150, thereby capturing movement of theelectrons created by the visible light. Since the electrons created byUV light radiated onto the light absorption layer 150 are much more thanthose created by visible light, current may flow in the device, withoutbeing captured by the low-current blocking layer 140. Accordingly, thephoto-detecting device of exemplary embodiments may have a higherUV-to-visible rejection ratio than the conventional UV light detectingdevice due to low responsivity to visible light. In particular, thephoto-detecting device according to exemplary embodiments may have aUV-to-visible rejection ratio of 10⁴ or more. Therefore, the device mayprovide a photo-detecting device with high detection efficiency andreliability.

FIGS. 3, 4, 5, 6, 7, and 8 are sectional views of a photo-detectingdevice at various stages of manufacture, according to exemplaryembodiments. Duplicative descriptions of the same components as thosedescribed with reference to FIGS. 1 and 2 will be omitted.

First, referring to FIG. 3, a second nitride layer 120 may be formed ona substrate 110. The second nitride layer 120 may include a nitridesemiconductor and may be grown by MOCVD. For example, the second nitridelayer 120 may be grown by injecting a Ga source and a N source into achamber at 550° C. and 100 Torr. Accordingly, the second nitride layer120 may include a GaN layer grown at low temperature. The second nitridelayer 120 may be grown to a thickness of about 25 nm. The second nitridelayer 120 grown to a small thickness at low temperature can provideimproved crystallinity and optical and electrical characteristics to afirst nitride layer 130 in the subsequent process.

Next, referring to FIG. 4, the first nitride layer 130 is formed on thesecond nitride layer 120 by MOCVD. The first nitride layer 130 mayinclude a nitride semiconductor and may be grown by MOCVD. For example,the first nitride layer 130 may be grown by injecting Ga source and Nsource into the chamber at 1050° C. and 100 Torr. In this manner, thefirst nitride layer 130 may include a GaN layer grown at hightemperature. Furthermore, the first nitride layer 130 may include ann-type-doped GaN layer obtained by injecting an additional Si sourceinto the chamber during growth of the first nitride layer 130, or mayinclude an undoped GaN layer. The first nitride layer 130 may be grownwith a thickness of about 2 μm.

Referring to FIG. 5, a low-current blocking layer 140 is formed on thefirst nitride layer 130. The low-current blocking layer 140 may includea multilayer structure. Here, the multilayer structure may be formed byrepetitively stacking at least one of binary, ternary, and quaternarynitride layers including (Al, In, Ga)N.

In exemplary embodiments, the multilayer structure of the low-currentblocking layer 140 may include at least two nitride layers havingdifferent composition ratios. The nitride layers included in themultilayer structure of the low-current blocking layer 140 may bedetermined depending upon compositions of a nitride layer to be includedin a light absorption layer 150. For example, when the light absorptionlayer 150 is to include an AlGaN layer, the multilayer structure of thelow-current blocking layer 140 may have a structure in which AlN/AlGaNlayers and/or AlGaN/AlGaN layers are repetitively stacked. When thelight absorption layer 150 is to include an InGaN layer, the multilayerstructure of the low-current blocking layer 140 may have a structure inwhich InGaN/InGaN layers, GaN/InGaN layers, and/or AlInGaN/AlInGaNlayers are repetitively stacked. When the light absorption layer 150 isto include a GaN layer, the multilayer structure of the low-currentblocking layer 140 may have a structure in which GaN/InGaN layers,InGaN/InGaN layers, and/or GaN/GaN layers are repetitively stacked. Themultilayer structure of the low-current blocking layer 140 may be formedby stacking three to ten pairs of nitride layers, and the low-currentblocking layer 140 may be formed to have a thickness of 10 nm to 100 nm.

Each of the at least two nitride layers having different compositionratios may be grown to a thickness of 5 nm to 10 nm, and may be grown tohave a different composition ratio by regulating an inflow rate of asource. It is also contemplated that the at least two nitride layershaving different composition ratios may be formed by stacking nitridelayers at different pressures of the chamber while preserving othergrowth conditions (e.g. growth temperature) including the inflow ratesof the sources. For example, when forming a multilayer structure inwhich an Al_(x)Ga_((1-x))N layer and an Al_(y)Ga_((1-y))N layer arerepetitively stacked, the Al_(x)Ga_((i-x))layer may be grown at apressure of about 100 Torr and the Al_(y)Ga_((1-y))N layer may be grownat a pressure of about 400 Torr. Under the same growth conditions exceptfor the pressure, the Al_(x)Ga_((1-x))N layer grown at a lower pressuremay have a higher Al ratio than the Al_(y)Ga_((1-x))N layer grown at ahigher pressure.

According to exemplary embodiments, the low-current blocking layer 140including the multilayer structure grown at different pressures asdescribed above may prevent (or otherwise reduce) the creation andpropagation of dislocations during the growth process, thereby improvingthe crystallinity of the light absorption layer 150 formed on thelow-current blocking layer 140. Furthermore, since the nitride layersgrown at different pressures having different composition ratios arerepetitively stacked, the stress caused, at least in part, by latticemismatch may be decreased, thereby also reducing the generation ofcracks in the light absorption layer 150. Moreover, since the nitridelayers are grown by changing only the pressure while preserving theinflow rate of the source, it may be relatively easy to form thelow-current blocking layer 140.

The multilayer structure of the low-current blocking layer 140 may begrown at a temperature between 850° C. and 1020° C. The growthtemperature of the multilayer structure of the low-current blockinglayer 140 may be 30° C. to 200° C. lower than that of the lightabsorption layer 150, and, therefore, the low-current blocking layer 140can have a higher defect concentration than that of the light absorptionlayer 150. Accordingly, the low-current blocking layer 140 may capturethe flow of electrons created by a reaction of the light absorptionlayer 150 to visible light.

Referring to FIG. 6, the light absorption layer 150 is formed on thelow-current blocking layer 140. The light absorption layer 150 mayinclude a nitride semiconductor and may be grown by selectively applyingelements and compositions of the nitride semiconductor depending upon awavelength of light to be detected by the photo-detecting device. Forexample, the light absorption layer 150 including a GaN layer or anInGaN layer may be grown for a photo-detecting device configured todetect UV light in the UVA band. The light absorption layer 150including an AlGaN layer having an Al ratio of 28% or less may be grownfor a photo-detecting device configured to detect UV light in the UVBband. The light absorption layer 150 including an AlGaN layer having anAl ratio of 28% to 50% may be grown for a photo-detecting deviceconfigured to detect UV light in the UVC band. It is contemplated,however, that exemplary embodiments are not limited thereto.

In exemplary embodiments, the light absorption layer 150 may be grown toa thickness of 0.1 μm or more, and thus the manufactured photo-detectingdevice may have improved photo-detection efficiency.

Referring to FIG. 7, the first nitride layer 130 may be partiallyexposed by partially removing the light absorption layer 150 and thelow-current blocking layer 140. In addition, a portion of the firstnitride layer 130 under the exposed portion may be further removed in athickness direction.

The light absorption layer 150 and the low-current blocking layer 140may be partially removed by photolithography and etching, for example,dry etching. It is contemplated, however, that any other suitablemethodology may be utilized in association with exemplary embodimentsdescribed herein.

Referring to FIG. 8, a Schottky junction layer 160 is formed on thelight absorption layer 150. The Schottky junction layer 160 may beformed by deposition (or other formation) of a substance including atleast one of ITO, Ni, Co, Pt, W, Ti, Pd, Ru, Cr, and Au. The thicknessof the Schottky junction layer 160 may be adjusted in terms of lighttransmittance and Schottky characteristics, and, may be, for example, 10nm or less in thickness.

In addition, the manufacturing method may further include forming a caplayer (not shown) between the Schottky junction layer 160 and the lightabsorption layer 150. The cap layer may be formed by growing ap-type-doped nitride semiconductor layer containing an impurity such as,for example, Mg. The cap layer may have a thickness of 100 nm or less,such as, 5 nm or less. The cap layer may improve the Schottkycharacteristics of the device.

Next, a first electrode 171 and a second electrode 173 are formed on theSchottky junction layer 160 and the exposed area of the first nitridelayer 130, respectively, as seen in FIG. 1. The first and secondelectrodes 171 and 173 may be formed by deposition (or other formation)of metallic materials and lift-off, and may also be composed of multiplelayers. For example, the first electrode 171 may be formed by stackingat least one of Ni and Au layers, and the second electrode 173 may beformed by stacking at least one of Cr, Ni, and Au layers. It iscontemplated, however, that exemplary embodiments are not limitedthereto.

FIG. 9 is a graph comparing responsivity of photo-detecting devicesdepending upon wavelengths, according to exemplary embodiments. Thephoto-detecting devices used in FIG. 9 include features of the exemplaryembodiments described herein. The UVA photo-detecting device includes aGaN layer as the light-absorption layer 150, the UVB photo-detectingdevice includes an AlGaN layer having an Al ratio of 28% as thelight-absorption layer 150, and the UVC photo-detecting device includesan AlGaN layer having an Al ratio of 50% as the light-absorption layer150.

The photo-detecting devices have high responsivity, as shown in FIG. 9.UV-to-visible light rejection ratios of the photo-detecting devices arecalculated on the basis of measurement results on responsivity obtainedby illuminating the photo-detecting devices with a white LED having apeak wavelength of 600 nm, and the calculation results show that all ofthese photo-detecting devices have UV-to-visible light rejection ratiosof 10⁴ or higher.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concept is not limitedto such embodiments, but rather to the broader scope of the presentedclaims and various obvious modifications and equivalent arrangements.

What is claimed is:
 1. A photo-detecting device, comprising: a firstnitride layer; a low-current blocking layer disposed on the firstnitride layer, the low-current blocking layer comprising a multilayerstructure; a light absorption layer disposed on the low-current blockinglayer; and a Schottky junction layer disposed on the light-absorptionlayer.
 2. The photo-detecting device of claim 1, wherein a defectconcentration of the low-current blocking layer is greater than a defectconcentration of the light-absorption layer.
 3. The photo-detectingdevice of claim 1, wherein the light absorption layer comprises at leastone of AlGaN, InGaN, AlInGaN, and GaN.
 4. The photo-detecting device ofclaim 3, wherein the multilayer structure comprises: at least one of abinary, ternary, and quaternary nitride layer comprising (Al, In, Ga)N;and at least two nitride layers of different composition ratios.
 5. Thephoto-detecting device of claim 1, wherein a thickness of the lightabsorption layer is in a range of 0.1 μm to 0.5 μm.
 6. Thephoto-detecting device of claim 1, wherein a thickness of thelow-current blocking layer is in a range of 10 nm to 100 nm.
 7. Thephoto-detecting device of claim 1, further comprising: a substrate, thefirst nitride layer being disposed on the substrate; and a secondnitride layer disposed between the substrate and the first nitridelayer, wherein the second nitride layer increases crystallinity of thefirst nitride layer.
 8. The photo-detecting device of claim 1, whereinthe first nitride layer comprises an undoped GaN layer or ann-type-doped GaN layer.
 9. The photo-detecting device of claim 1,further comprising: a cap layer disposed between the light absorptionlayer and the Schottky junction layer, wherein the cap layer comprisesan Mg-doped nitride layer.
 10. The photo-detecting device of claim 1,further comprising: a first electrode disposed on the Schottky junctionlayer; and a second electrode disposed on an exposed region of the firstnitride layer, wherein the light absorption layer and the low-currentblocking layer are removed in the exposed region.
 11. Thephoto-detecting device of claim 1, wherein a UV-to-visible lightrejection ratio of the photo-detecting device is greater than or equalto 10⁴ at a peak wavelength of visible light of 600 nm.
 12. A method ofmanufacturing a photo-detecting device, the method comprising: forming afirst nitride layer; forming a low-current blocking layer comprising amultilayer structure on the first nitride layer; forming a lightabsorption layer on the low-current blocking layer; and forming aSchottky junction layer on the light absorption layer, wherein thelow-current blocking layer is formed at a lower temperature than thelight absorption layer.
 13. The method of claim 12, wherein thelow-current blocking layer is formed at a temperature 30° C. to 200° C.lower than a formation temperature of the light absorption layer. 14.The method of claim 12, wherein: the multilayer structure comprises atleast one of a binary, ternary, and quaternary nitride layer comprising(Al, In, Ga)N; and the multilayer structure is formed by repetitivelystacking at least two nitride layers of s different composition ratios.15. The method of claim 14, wherein the at least two nitride layers areformed at different ambient pressures.
 16. The method of claim 15,wherein a temperature and an inflow rate of a source gas used to formthe at least two nitride layers are held substantially constant whilethe at least two nitride layers are being formed.
 17. The method ofclaim 12, further comprising: forming a second nitride layer on asubstrate, wherein the first nitride layer is formed on the secondnitride layer, the second nitride layer being disposed between the firstnitride layer and the substrate, wherein the second nitride layer isformed at a lower temperature than the first nitride layer.
 18. Themethod of claim 12, further comprising: forming, before forming theSchottky junction layer, a cap layer comprising an Mg-doped nitridelayer on the light absorption layer.
 19. The method of claim 12, furthercomprising: exposing, before forming the Schottky junction layer, aportion of the first nitride layer by removing corresponding portions ofthe light absorption layer and the low-current blocking layer.
 20. Themethod of claim 19, further comprising: forming a first electrode on theSchottky junction layer; and forming a second electrode on the portionof the first nitride layer.